The vehicle-to-vehicle communication system in recent years has, or allows, each of the vehicles in the system to transmit and receive communication packets in sequence to/from other vehicles in the system for exchanging vehicle information about the travel speed, the current position, the travel direction and the like among a self-vehicle and the other vehicles.
Further, a drive support apparatus used in such vehicle-to-vehicle communication system is devised, or is proposed, to support a drive operation of the vehicle in the system according to a predicted collision possibility between the self-vehicle and the other vehicles in various manners.
For example, in a patent document, JP 2008-126755 A (patent document 1, a drive support apparatus is disclosed that is capable of (i) determining whether a currently-traveled road traveled by the self-vehicle (i.e., a self-vehicle travel road, hereafter) is a priority road over the other road traveled by the other vehicle (i.e., an other vehicle travel road) and (ii) changing basis for calculation of the collision possibility based on a determination result of the priority road.
More practically, when it is determined that the self-vehicle travel road is a priority road over the other vehicle travel road(s), in comparison to a situation when the self-vehicle travel road is determined as a non-priority road, the calculation of the collision possibility is based on a condition that is less likely to predict a collision of the two vehicles.
Then, in case that it is determined that the self-vehicle may collide with a certain other vehicle at a certain intersection, i.e., when the self-vehicle and the other vehicle may have an upon-meeting collision at a certain intersection, information for avoiding such a collision with the certain other vehicle is output as support information.
Note that a priority road in the above context means that, when plural roads are connected to, e.g., intersecting with, each other, the traffic (i.e., a flow of the vehicles) on the priority road is configured to be less obstructed, or more prioritized, than other roads. Further, a non-priority road means that, when a non-priority road is connected to a priority road, the traffic on the non-priority road is less prioritized than priority road. Among the plural connected roads, which one of those roads serves as a priority road is predetermined as a road structure.
According to the drive support apparatus of the patent document 1, when the self-vehicle travels on a priority road, the support information for supporting the self-vehicle is made less noticeable, i.e., is less likely to be output/notified to the driver, than when the self-vehicle travels on a non-priority road.
Note that, when the self-vehicle travels on a priority road, the other vehicle which may have an upon-meeting collision with the self-vehicle is a which traveling on a non-priority road.
According to the drive support apparatus of the patent document 1, when the self-vehicle travels on a priority road, the drive support apparatus is capable of suppressing an output of the support information for notifying the self-vehicle of the other vehicle which is traveling on a non-priority road.
Note that an idea of stricter support information output condition for the self-vehicle on a priority road is based on an assumption that the other vehicle on a non-priority road should be or is expected to decelerate/yield for a vehicle on a priority road, i.e., to perform a collision avoidance behavior, according to a traffic regulation or the like. In other words, the driver of a vehicle on the non-priority road is assumed to act, i.e., to recognize, determine, and operate, in an appropriate manner according to a traffic situation on the priority road.
However, traveling on a priority road does not necessarily mean that the support information regarding the other vehicle on a non-priority road is not needed.
For example, when the visibility of the field around, i.e., of a road in front of, the self-vehicle is bad (i.e., compromised), such as a travel in a foggy night, the driver of the vehicle on a non-priority road may not appropriately recognize the existence of the self-vehicle, which may further lead to an in-appropriate merging operation of the other vehicle from the non-priority road into the self-vehicle travel road, based on a wrong recognition that the traffic on the priority road is sparse and “allowing.”
Therefore, in case that the field/environmental visibility is relatively bad, the support information regarding the other vehicle traveling on the non-priority road may preferably be output for the driver of the self-vehicle, even when the self-vehicle travel road is a priority road.
Further, at a signal device equipped intersection, a travel right of the intersection may be given to the vehicle on the non-priority road by a display of the signal. That is, even when the self-vehicle travel road is a priority road, during a time when a travel right of the intersection is not given to the self-vehicle by the signal device, the support information regarding the other vehicle traveling on the non-priority road should be output for the driver of the self-vehicle, in order for him/her to prompt a deceleration/stop operation of the self-vehicle.
That is, whether to output the support information regarding the other vehicle traveling on the non-priority road should be output also depends on a display state of the signal device at an intersection.